Author Topic: Don Sachs Tube Preamp and Amplifier  (Read 14333 times)

Offline mresseguie

  • Obsessively Audiophilic
  • ****
  • Posts: 392
Re: Don Sachs Tube Preamp and Amplifier
« Reply #30 on: November 26, 2019, 07:47:09 AM »
Hello, Don.

Thanks for posting the pic! That's sweet looking. Is the preamp in Jim's (Blueone's) system?

Does this newest version not have gain controls, or are they still an option? I really like my ability to dial down the gain.

I won't have an opportunity to do it this year, but I think I'm going to ship my Model 2 back to you for an upgrade next year - perhaps in April. Let's see....Polish caps, rectifier tube change, etc. to bring it up to 'top of the line' status.

Daedalus Audio Apollos; Fritz Loudspeakers LS/5-R
dB Audio Labs Tranquility SE DAC w/Jupiter Caps
Don Sachs Model 2
Don Sachs Kootenay 120 KT88; IdeEdge 1200as2
TWL loom
PI Audio UberBUSS, DigiBUSS, Uber-MiniBUSS, USB cable
Mac Mini

Offline dls123

  • Seeking Help
  • **
  • Posts: 26
Re: Don Sachs Tube Preamp and Amplifier
« Reply #31 on: November 26, 2019, 08:50:31 AM »
Sure, send it whenever and I can improve it.  I have dropped the channel attenuators and gone to relay input switching because I can shorten the signal path by at least a foot.   Inputs go about 3-4 inches to the relay/attenuator and then only about 5 inches down to the preamp section.  The attenuators are not needed unless you need a balance control.  I worked with Arek to dial this khozmo version in such that the taper is perfect for this preamp, pretty much for any amp and speaker combo.   THere is only one resistor in the signal path for any volume setting on each channel.  Essentially like no volume control at all, except that you have one:)


Offline dls123

  • Seeking Help
  • **
  • Posts: 26
Re: Don Sachs Tube Preamp and Amplifier
« Reply #32 on: May 02, 2020, 08:50:43 PM »
Hi all...
I am almost finished with the next project.  It is a tube integrated amp.  It will have the OLED Khozmo 64 step remote attenuator with relay input switching, exactly as used in the latest version of the line stage.   The case is wooden and it looks very much like the Kootenay 120 power amp with transformers and tubes on top.   Same epoxy potted Polish transformers in the stainless steel cans, but optimized for the 6L6 rather than KT88 tubes.   It will be 25-30 watts/ch and have the same auto bias and fully regulated power supply as in the bigger amp, but scaled down for the 6L6 tube.
 The input and driver tubes are 6SN7 types as in the big Kootenay amp.   The prototype was very, very good and it was only about 20 watts/ch using an off the shelf Antek power transformer.  Sounded like a 60 watt/ch amp on my 96 dB speakers.  The 6L6 is just a wonderful tube and I have always loved them since my Citation V days.  There is a great Russian version of the tube that I will supply with the amp.   The production version of the integrated has a custom wound toroid power transformer that is slightly smaller than the one in the Kootenay 120 amp, but will be 20-30% larger than it needs to be to drive the 6L6 tubes to clipping at 25-30 watts/ch.  I now have all the parts and expect to have the first production one completed within 30 days.   I will post photos on my site.   It will have 1 xlr input pair and 3 rca inputs, and the usual 4 and 8 ohm taps on the output transformers.  Not sure of the exact price yet because I need to see how long the build time is, but in the range of $3499-3799.   This integrated should give maybe 80-90% of performance of  the separates as long as your speakers are tube friendly and fairly efficient so that 25-30 watts/ch is adequate headroom.  Perfect for full range drivers, efficient box speakers such as the Zu speaker line, and of course the entire Spatial Audio line of speakers.   Really anything more efficient than 90 dB or so.  Stay tuned.....